Devices are already available commercially to test the concentration of luteinizing hormone (LH) in human urine. Typically these devices provide a coloured signal readable by eye, the intensity of which alters with increasing LH concentration. Examples are described in EP-A-291194 and EP-A-383619. A series of regular tests, for example daily tests, are conducted during the cycle to pinpoint the LH surge or LH peak that is associated with the event of ovulation. This information is used to assist conception. It indicates the brief time in the ovulation cycle during which natural insemination is most likely to result in pregnancy. The information is also useful to health professionals conducting IVF treatments.
Although the existing tests make a valuable contribution in this area, the essentially transient nature of this physiological indicator can cause the ovulation event to be missed.
Moreover, at least in some individuals, comparatively high LH concentrations may be observed at times in the cycle not associated with the event of ovulation. This may occur for example due to gross variations in urine concentration. High LH concentrations arising from such causes can be wrongly associated with the event of ovulation.
Accordingly there is a need for improved test methods and test kits that enable ovulation to be pinpointed more accurately and for the likelihood of false indications to be reduced.
Ways of monitoring the mammalian ovulation cycle, primarily for the purpose of contraception, using analytes such as LH and estrone-3-glucuronide (E3G) are described in EP-A-656118, EP-A-656119 and EP-A-656120.
It has previously been proposed to use E3G (also in conjunction with LH) as an indicator of fertility status primarily for the purposes of contraception, although such information can also be used to assist conception if desired. In WO 95/01128 a base line E3G level is established at the start of an ovulation cycle and used as a reference against which to compare subsequent E3G signals to detect a rise indicative of the commencement of the fertile phase. For the avoidance of conception an adequately early warning of the onset of the fertile phase must be given, and an E3G rise associated with that onset will be much lower than is desirable for the purposes of the present invention. In the present invention, the objective is to pin-point as accurately as possible the time of maximum fertility. Accordingly, the optimum ratio between an E3G test signal and the base line signal in the present context would be quite inappropriate for the purposes of contraception.